The invention relates to a liquid crystal display device provided with a reflection sheet on the back side and a method of fabricating the reflection sheet.
A liquid crystal display device provided with a reflection sheet for effecting a display utilizing reflection of an external light is frequently used by miniature electronic equipment, and the like.
FIG. 3 is a sectional view showing the construction of an example of a conventional reflection type liquid crystal display device 10. The liquid crystal display device 10 generally comprises glass plates 11, 12, liquid crystal 13 which is enclosed between the glass plates 11, 12, and an adhesive 16 for sealing the liquid crystal 13, and polarization plate 14, 15 attached to the outside of the glass plates 11, 12. In such a liquid crystal display device, a colored reflection sheet 2 is bonded onto a back side of a panel by an adhesive 3 for coloring the back ground of the panel.
The reflection sheet used in a conventional liquid crystal display device is formed by color printing on a white original plate or blank made of resin, e.g., polyester by an appropriate size to form plural reflection sheets, coating an adhesive on the original plate e.g., by screen printing so as to bond the reflection sheets onto glass plates of the liquid crystal display device. However, the adhesive used conventionally has no color, and hence there are following problems.
(1) When the adhesive is coated on the original plate, e.g. by screen printing, if there is a pinhole on a plate for printing, or if there occurs the flying of the adhesive when peeling off the screen after printing, the adhesive is prone to stick to an unwanted portion of each reflection sheet, which is however hardly detected.
(2) If the reflection sheet is bonded to the polarization plate 15 in a state where there occurs the flying of adhesive on the reflection sheet, the adhesive appears as a black point, causing a problem that the liquid crystal display device becomes defective.
(3) When the reflection sheet is prepared from the original plate, e.g. by a punching process, or colored printed portion of the original plate and a plate for printing an adhesive are aligned with each other, the operations thereof are not easily effected if the adhesive has no color and also the position of the adhesive is hardly read out by a camera, and hence it is impossible to employ a machining method for machining the components on the basis of data read out by the camera.
The invention has been made in view of the problems of the conventional liquid crystal display device, and it is an object of the invention to fabricate a reflection sheet automatically by easily detecting the sticking of an adhesive onto an unwanted portion of the reflection sheet, easily aligning between the colored printed portion of an original plate and a plate for printing an adhesive, and reading out a coating state of the adhesive by a camera.
To achieve the above object, a liquid crystal display device having a reflection sheet bonded onto the back side thereof according to the first aspect of the invention is characterized in that a reflection sheet is bonded onto the back side by an adhesive which is different from the reflection sheet in color.
A method of fabricating a reflection sheet of the liquid crystal display device according to the second aspect of the invention is characterized in comprising the steps of printing and forming multiple colored portions and an alignment mark on an original plate, coating each colored portion with a colored adhesive at a given position while the alignment mark serves as a reference position, and cutting the colored portion coated with the adhesive from the original plate.
The method of fabricating a reflection sheet of the liquid crystal display device according to the third aspect of the invention is characterized in that in second aspect of the invention a screen for printing the adhesive is aligned with the alignment mark serving as a reference position and the colored portion is coated with the colored adhesive at a given position.